Chemical equations symbols used

Because of the additional complexity introduced into chemical equations by use of H3O+ in place of H+, it is customary for the sake of convenience to write equations for reactions of acids in aqueous solution with use of the symbol H +. It is to be understood that this is a shorthand device, and that the molecular species present is the hydronium ion, H3O +. ... 

Chemical equations are used to represent reactions. They are written using symbols and formulas for elements and compounds. Once the symbols and formulas are written, the equation can be balanced only by changing coefficients. 

Let s say that in the laboratory, nickel chloride (NiCl2) and sodium hydroxide (NaOH) are dissolved in water, producing a precipitate of solid nickel hydroxide [Ni(OH)2] plus sodium chloride (NaCl) dissolved in water. This description is important because it tells exactly what is going on in the reaction, but a simpler way of expressing this reaction is with a chemical equation, which uses formulas and symbols to describe the same reactions. 

FIGURE 1.3 The three levels of studying chemistry and their relationships. Observation deals with events in the macroscopic world atoms and molecules constitute the microscopic world. Representation is a scientific shorthand for describing an experiment in symbols and chemical equations. Chemists use their knowledge of atoms and molecules to explain an observed phenomenon. 

Symbols indicating the physical state of each reactant and product are often shown in chemical equations. We use the symbols (g), (/), (s), and (aq) for gas, liquid, solid, and aqueous (water) solution, respectively. Thus, Equation 3.4 can be written... 

The reactions that we discuss in this chapter will be represented by nuclear equations. An equation of this type uses nuclear symbols such as those written above in other respects it resembles an ordinary chemical equation. A nuclear equation must be balanced with respect to nuclear charge (atomic number) and nuclear mass (mass number). To see what that means, consider an equation that we will have a lot more to say about later in this chapter ... 

A chemical equation typically also shows the physical state of each reactant and product by using a state symbol ... 

A note on good practice The chemical equations for elementary reaction steps are written without the state symbols. They differ from the overall chemical equation, which summarizes bulk behavior, because they show how individual atoms and molecules take part in the reaction,. We do not use stoichiometric coefficients for elementary reactions. Instead, to emphasize that we are depicting individual molecules, we write the formula as many times as required. 

These examples suggest that the learner is not always aware which aspects of our use of symbolic representation in chemistiy are intended to be significant. This is an area where further work would be useful, as clearly teachers need to do more to induct learners into the intended symbolism we use in teaching the subject. In the next section, these issues will be explored further in the particular context of learning about chemical equations. 

Given this context, the use of chemical symbols, formulae and equations can be readily misinterpreted in the classroom, because often the same representations can stand for both the macroscopic and sub-microscopic levels. So H could stand for an atom, or the element hydrogen in an abstract sense H2 could mean a molecule or the substance. One common convention is that a chemical equation represents molar quantities, so in Example 9 in Table 4.1,... 

Students ability to connect observations at the macroscopic level with their descriptions using the submicro and symbolic types of representation improved as a consequence of the LON teaching approach. Teachers attributed the improvement to the consistent use of all three types of representation and to the use of visible models as a tool for bridging the gap between macroscopic observations and symbolic notations of chemical equations. 

Point defect populations profoundly affect both the physical and chemical properties of materials. In order to describe these consequences a simple and self-consistent set of symbols is required. The most widely employed system is the Kroger-Vink notation. Using this formalism, it is possible to incorporate defect formation into chemical equations and hence use the powerful methods of chemical thermodynamics to treat defect equilibria. 

We use F as a representative molecular structure of the fuel in terms of its atoms and P, a similar description for the product. Of course, we can have more than one product, but symbolically we only need to represent one here. The chemical reaction can then be described by the chemical equation as... 

Using Lewis symbols, write a balanced chemical equation showing the formation of lithium fluoride, LiF, from isolated lithium and fluorine atoms. 

If you had to write a math equation, you probably wouldn t write, Twenty-eight plus fourteen equals forty-two. It would take too long to write and it would be hard to read quickly.You would write, 28 + 14 = 42. Chemistry is the same way. Chemists have to write chemical equations all the time, and it would take too long to write and read if they had to spell everything out. So chemists use symbols, just like we do in math. 

Table 8-1 Symbols Commonly Used in Chemical Equations...

In this expression, the n are the stoichiometric coefficients in the chemical equation and the symbol 2 (sigma) means a sum. The first sum is the total enthalpy of formation of the products. The second sum is the similar total for the reactants. Toolbox 6.2 explains in more detail how to use this expression. 

Chemical equations can also be written using chemical symbols. Chemical symbols are a shorthand way to write the name of an element. The chemical symbol for hydrogen is H, and the chemical symbol for oxygen is O. 

The reactant side of this chemical equation, using chemical symbols looks like this ... 

Chemical symbols are used to describe atomic and molecular structures and how they appear in chemical changes. A chemical equation describes a chemical change. The chemical symbols in the equation show the atomic structures of the reactants and products. Hieroglyphs are merely pictures and do not show atomic and molecular structure. 

Some additional information that can be conveyed in a balanced chemical equation (s) = solid, (g) = gas, (aq) = aqueous, and (1) = liquid. The following equation shows the proper use of these symbols S(s) + 6HN03(aq) —> H2S04(aq) + 6N02(g) + 2H20(1). It should be noted that [aq] means aqueous solution and [1] means in the liquid phase of a pure substance. Use phase-indicating symbols in your balanced equation in no. 3 above. 

The triplets p, q, r are known as the stoichiometric coefficients of the chemical components in the formation equation of the complex, and are often quoted as subscripts next to the symbol used for the formation constant, which in this case is (3, so that the equilibrium formation constant would be defined as... 

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